Apple’s Foundation TV series has lost one of its showrunners. Co-showrunner Josh Friedman has exited the upcoming series adaptation of Isaac Asimov’s groundbreaking sci-fi novels, leaving co-writer David S. Goyer as the sole showrunner of this ambitious, long-awaited project.

The Wrap reports that Friedman has stepped down from the day-to-day responsibility of acting as a Foundation TV series showrunner, but will remain attached as an executive producer. That leaves David S. Goyer, who was co-writing the series with Friedman, as the sole showrunner on the Skydance Television-produced project.

The is the second time that Friedman has left a project as showrunner — he was previously replaced as the showrunner on TNT’s adaptation Snowpiercer by Orphan Black co-creator Graeme Manson. However, the War of the Worlds writer still retains his executive producer credit for Foundation, so it seems he’ll stay involved in some capacity.

Foundation has proven to be a difficult story to crack. Over the years, countless attempts to adapt Asimov’s dense, sprawling series have been made, including an expensive feature adaptation from New Line, a version helmed by Roland Emmerich under Columbia Pictures and Sony, and a TV series adaptation from HBO by Jonathan Nolan. None of these came to fruition, and instead the rights passed over to Skydance, which struck a deal with the Asimov estate and hired Goyer and Friedman in 2017. Apple soon picked up the series for its highly anticipated streaming service, Apple TV+.

The complex saga is as difficult to summarize as it has been to adapt, so here is the Wikipedia summary:

The premise of the series is that the mathematician Hari Seldon spent his life developing a branch of mathematics known as psychohistory, a concept of mathematical sociology. Using the laws of mass action, it can predict the future, but only on a large scale. Seldon foresees the imminent fall of the Galactic Empire, which encompasses the entire Milky Way, and a dark age lasting 30,000 years before a second great empire arises. Seldon’s calculations also show there is a way to limit this interregnum to just one thousand years. To ensure the more favorable outcome and reduce human misery during the intervening period, Seldon creates the Foundation – a group of talented artisans and engineers positioned at the twinned extreme ends of the galaxy – to preserve and expand on humanity’s collective knowledge, and thus become the foundation for the accelerated resurgence of this new galactic empire.

The Apple TV series has the benefit of receiving the blessing of the Asimov estate, with Robyn Asimov — Isaac’s daughter — serving as executive producers alongside David Ellison, Dana Goldberg, Marcy Ross and now Friedman.